Motor fuel



Oct. '17, 1944.

' DEGREES SPARK ADVANCE s Sheets-Shet 1 ENGINE R.P.M.

Fig.1

' INVENTORS. Wzlllam B. 085- BY Kenneth B0 dl at I J/V/ ATTORNEY.

Oct. 17, 1944.

DEGREES SPARK ADVANCE w. B. ROSS ETAL 2,360,585

MOTOR FUEL Filed Oct. 27, 1941 s Sheets-Sheet 2 I000 I500 2000 2500 30003500 D ENGINE REM.

Fiy. 2

INVENTORS.

William 5.13055 BY Kennel'h B0ldZ-' ATTORNEY. EAL/n4, A" ((1 A 7 Oct.17, 1944.

DEGREES SPARK ADVANCE w. B. ROSS mm 4 2,360,585

MOTOR FUEL Filed Oct. 27, 1941 3 Sheets-Sheet 3 ENGINE REM.

INVENTORS William 5.12055 BY Kenneth Boldl' 4 7 ATTORNEY.

Patented Oct; 17, 1944 UNITED' STATES PATENT OFFICE MOTOR FUEL WilliamB. Boss, Evanstomcand Kenneth Boldt, Highland Park, Ill., assignors toThe Pure Oil Company, Chicago, Ill. a corporation of Ohio ApplicationOctober 27, 1941, Serial No. 416,656 8 Claims. (CL 44-80) This inventionrelates to motor fuels for internal combustion engines and particularlyto automotive gasoline fuels having superior performancecharacteristics. The invention is particularly-directed to providingmotor fuels having high susceptibility to improvement by the addition ofmetallo-organic anti-knock agents such as lead tetraethyl and havinghigh anti-knock quality as well as balanced distillationcharacteristics. 10

Among the qualities which characterize good gasoline, high anti-knockrating has probably motor fuels, and for this purpose many substanceshave been incorporated in gasoline. For example, metallo-organiccompounds, benzol and various alcohols have been utilized. Morerecently, olefin polymers such as the polymers of in general have beenfound to be much more susceptible to anti-knock improvement by theaddition of tetraethyl lead than oleflnic and aromatic hydrocarbons, thelead susceptibility being greatest in the parafilns and diminishing inthe other hydrocarbons in the order named.

It has been found that the unusual improvement in performance ofinternal combustion engines effected by motor fuels in accordance withthis invention is notfully indicated by the usual anti-knock ratingdetermination, due to deficiencies inherent'in the available recognizedmethods of testing. Many methods and a rather large number of deviceshave .been proposed for the evaluation of motor fuels by knockingtendencies. Probably the best-known testing devices are the Ricardovariable compression engine, the Ethyl Gasoline Series 30 engine,'andthe Cooperative Fuel Research engine, usually called C. F. R.

olefins containing from two to five carbon atoms The engine is o t y ine have been widely used in commercial motor fuels with great advantage.These materials'can be prepared from the waste gases produced in thecracking of petroleum oil. The anti-knock properties of the olefinpolymers may vary greatly depending upon such factors as the method ofmanufacture and the particular olefin used. However, it is a generalpractice today to add lead tetraethyl to hydrocarbon base stocks inorder to bring the resultant fuel blend to a uniform high anti-knockvalue.

' Studies of the problem of motor knock and of motor fuel compositionshave revealed thatthe tendency of a motor fuel'to cause engine knock isa function of the fuel composition as well as of engine conditions. Ithas been found that in general, anti-knock value of a homologous seriesof hydrocarbons depends upon the number of carbon atoms in-the moleculesand the compactness of the molecular structure, the antiknock valueincreasing with numerical decrease and centralization of carbon atoms.The effect of tetraethyl lead on the anti-knock value of motor eral usetoday than any other engine for antiknock' testing purposes. The mostwidely used method o'f'determining the knocking tendency with the C. F.R. engine is one which has been standardized and recommended by theAmerican Society for Testing Materials. This is known as the A. S. T. M.Motor Method and is designated Method D 357-40. Results of 4 tests bythe A. S. T. M. Motor Method using the C. F. R. engine are reported interms of octane numbers. Octane number of a motor, fuel is numericallyequivalent to the percent by volume of iso-octane (2, 2, 4 trimethylpentane) in a mixture of isooctane and normal heptane, that is equal in-5 knocking. tendency to the fuel under test, the better fuels having thehigher numerical values. Unless otherwise indicated, all octane numbersini; From the inception of the method of testing motor fuels bymeasurement of knocking tend-- ency, there has .been and still is aconsiderable r discrepancy between the rating of fuels as deterfuels hasalso been studied and a characterizing mined by the'various testingmethods. Furtherfactor called lead susceptibility has been introduced.By this factor, fuels may be evaluated in terms of the. improvement inanti-knock value effected by a given addition of tetraethyl lead.

more, and of' probably stillgreater importance, is the fact that therestill .prevails 9. probably greater discrepancy between the ratings ofmotor fuels asfdetermined by any ,of the foregoing It has beenestablished that some gasolines show methods a d the rating of motorfuels as determore improvement in anti-knock ratingfor a given additionof tetraethyl lead than do others. This variation in susceptibility hasbeen found to be related. to the composition of the fuel. For

I mined by actual road performance tests. One

prominent factor, if not the mostprominent ;factor, that contributes tothe latter discrepancy V is the fact that the prevailing testingmethodsv example, paraflinc and naphthenic hydrocarbons require theoperationof the testing engines at constant speed and under constantload, whereas the knocking tendency of automotive engines in actualoperation is greatest during periods of acceleration. Since the unusualcharacteristics of motor fuels in accordance with this invention aremanifest under conditions of engine acceleration, it'is apparent thatthe usual laboratory testing methods are of little value in evaluatingsuch fuel. The only entirely satisfactory method known at the presenttime is a much more time-consuming and expensive test carried out instock automotive engines under conditions of actual road performance.This test is called the Road rating test. The additional time andexpense involved is believed to be justified by the fact that theresults of such tests are final and conclusive as to the value of amotor fuel in actual service.

The road rating test consists of the evaluation of motor fuels by meansof determining the knocking tendency of standard automobile engines whenusing the particular test fuel under conditions of actual accelerationperformance on the road. Since it is generally accepted 'that knockingis an indication of inefiicient operation, those fuels that show theleast tendency to knock are the superior fuels. Through the use ofproper instruments and replacing the standard'automatic distributor witha manually controlled distributor, the speed attained under fullthrottle acceleration at which the knock dies out for a given sparkadvance is determined. This test is repeated for a number of differentspark advances. By plotting the highest spark advance attainable withoutevidence of knocking against R. P. M. of engine or car speed in milesper hour, a curve is'obtained which when compared ,with a curve showingthe standard spark advance setting of the engine in which the tests aremade, indicates whether or not a given fuel may be expected to knock atvarious speeds in that particular car when operated with a standardspark advance setting. These determinations are generally made instandard motor cars (with the exception of the distributor) underconditions of actual road operation. However, in order to satisfactorilyevaluate fuels of unusually high quality, it has been necessary tomodify the stock engines by replacing the usual heads wlthheads having ahigher compression ratio.

It is an object of this invention to provide motor fuels having greatlyimproved performance characteristics.

It is another object of this invention to provide improved motor fuelshaving high road rating test values at all speeds.

It is still another object of this invention to provide improved motorfuels which exhibit superior high and low speed performancecharacteristics in internal combustion engines, particularly duringperiods of acceleration;

A further object is to provide improved motor fuels in which thechemical composition-boiling range characteristics are controlled withina definite fixed relation.

A still further object is to provide improved motor fuels havingunusually high susceptibility to improvement in road performance byaddition of lead tetraethyl.

These and other objects of the invention will be apparent from thefollowing detailed description considered in connection with theaccompanying drawings, all of the figures of which are graphs showingborderline knock-test results obtained with various motor fuels.

It has been established that vastly improved road performancecharacteristics at low speed in internal combustion engines can besecured by incorporating in motor fuel used in internal combustionengines, olefin hydrocarbons boiling within the approximate range of toF. and having an A. S. T, M. Motor Method octane blending value notsubstantially less than 110.

As a result of extensive tests in actual motor car operation, it hasbeen found that the modem automobile engine performance under conditionsof low speed acceleration is closely related to the composition of thelow boiling portion of the motor fuel used in the engine, that is, theportion boiling not substantially above 140 F.

.Likewise,'it has been found that the high speed performance of theengine is most closely related to the composition of the higher boilingportion of the motor fuel used in the engine, that is, the portionboiling above about 235 F.

The intermediate portion of the fuel boiling between approximately 140F. and 235 F. may

contain any convenient mixture of hydrocarbons so long as the overalloctane of this fraction is sufiicient to produce the desired overalloctane in the finished motor fuel. The proportions of the low boiling,intermediate and high boiling fractions which are used are such as toproduce a'balanced volatility in the final fuel. An unusually largeproportion of either the light fraction or the heavy fraction would leadto uneven carburetion and consequent loss of efficiency in motorperformance. A fuel of well balanced volatility capable of producingparticularly good all speed performance preferably contains about 8 to30% by volume of, the low boiling fraction,

about 20 to 50% by volume of intermediate frac-' tion, and about 35 to70% by volume of high boilingfraction. It will be appreciated that afairly wide tolerance in the proportions of these fractions is requiredin order to prepare motor fuels, the volatility of which is adapted tosatisfactory engine operation under both high temperature and lowtemperature operating conditions.

,It has now been found that motor fuels containing predominant amountsof unsaturated hydrocarbons in the low boiling range and not more thanminor amounts of unsaturated hydrocarbons particularly unsaturatedaliphatic hydrocarbons in the high boiling range, 1. e. less than 25%and preferably less than 10% by volume, produce exceptionally good lowand high speed performance in internal combustion en;- gines andparticularly those engines of high compression ratios such ascompression ratios of about 6.521 to 9:1. This is particularly true whenthe high boiling'portion of the fuels contains substantial amounts, forexample, about 30% or 50% or more by volume of alkylated benzenehydrocarbons. In the low boiling range those unsaturated hydrocarbonssuch as monooleflns having a minimum tendency to form undesirable gumsare preferred. The maximum boiling points of the constituents in thehigh boiling fraction should be such that when the constituents areblended with the remaining components of themotor fuel, the end point ofthe blended fuel will not be substantially in excess of that of ordinarycommercial gasoline which at the present time is in the neighborhood of400 F. The minimum boiling point of the constituents in the low boilingfraction is largely dependent upon the vapor pressure of theconstituents and the characteristics of the remaining fractions of themotor fuel with which the I 2,360,585 low boiling materials 1m blended.Excessive the desired limits and road rating test data on blending 50%of a mixture of low boiling straight run gasoline obtained from Coronadocrude oil these fuels obtained. In considering these data,

it shouldbe borne in mindthat not only the road anti-knock qualities ofthe base gasoline are important, but in addition the response of ,thefuels to additions of lead tetraethyl are also of great importance sincemost commercial motor fuels have this anti-knock agent added to them ito secure and maintain the desired level of antiknock value in thefinished fuels. It is essential that the leaded fuel as well as thehydrocarbon motor fuel base show the desired road performancecharacteristics. The data in Table I show the boiling range-chemicalcomposition relationship of the fuels employed in the road rating tests.

Table I g Percent by volume of traction Fue y vo Fraction f? Parai-Naph- Ole- Aroiins thenes fins matics B. P.140 F- 8 86 14 0 2 140-235 F71 72 26 0 2 15-16. P 21 59 24 0- 17 B. P.-l40 F. 17 48 0 52 0 3 Mil-235F... 25 25 17 46 13 E. P 59 35 6 8 61 I B. P.-l40 F, 16 79 0 21 0 4(i-B" F"--- 41 14 50 4 33 E. P 43 35 14 9 42- B. P.140 F 22 27' 0 73 0 5140-235" F 33 20 18 59 3 E. P 45 0 68 23 8 B. P.-1.40 F 21 71 0 29 0 8140%5 F---" 87 41 20 39 0 E. Pi -42 33 26 27 14 B. P.-140 F- 8 88 12 0 0-19. Mil-235 E--- 40 29 60 7 4 I E. P 52 27 19 11 43 I B. P.-l40 F- 14.38 0 62 0 15-20- 140235 F"--- 34 m 11-. 51 12 235-E. 1 152 24 12 1e 43Fuel 2 is a blend of standard reference fuels, A-6 (23%) and 0-12 (77%)to produce a '70 octane number blended fuel. This fuel was used in thetests as a reference fuel and to show that octane number alone is notindicative of the performance characteristics of a motor fuel. Fuel 3was prepared by blending 50% by volume of the I. B. P.2'l5 F. fractionof vapor phase thermal.

and 14 pound Reid vapor pressure casing head gasoline with 50% by volumeof a mixture containing approximately 90% hydroformed gasoline boilingbetween 235 and 400 F. and :about 10% of a commercial grade of xylene.This fuel had an octane number of 75.3. Fuel E-20 was prepared byblending 50% by volume of the I. B. P. to 235 F. cut of vapor phasethermal cracked gasoline with 50% by volume ofthe same heavy fraction aswas used in fuel E-19. Fuel E-20 had an octane number of 75.6. In the235ELP. fraction of all of the fuels, the- Aromatics indicated in TableI are alkyl benzenes. The analysis 'of the fuels for the'determinationof the parafflnic, naphthenic, olefinic andaromatic constituentswas-carried out in accordance with the method described by Kurtz andHeadington, Ind. Eng. Chem., Anal. Ed. 9,

The curves shown in Figures 1, 2 and 3' forming a part of thisspecification are curves obtained by the borderline knock test methodwhich is described by Campbell, Greenshield and Holaday in the Journalof the Society of Automotive Engineers, vol. 48, page 193, 1941. Thesecurves clearly shovy the ability of a fuel to tolerate spark advanceswithout knocking throughout the usual operating speed range. Theborderline knock test curves indicate the line which is drawn be? tweensatisfactory and unsat sfactory engine operation. When the borderlineknock test curve is compared with a curve showingjthe standard sparkadvance, the vertical distance between the curves is a measure of theperformance quality of tory or non-knocking operation is obtained,

whereas when the borderline curve is below the standard spark advancecurve, unsatisfactory or knocking performance is obtained. Becauseof theunusually good performance characteristics of some of the fuels tested,special high compression,

- been included except in Figure 1, since the standcracked gasoline with50% by volume of a- 200 cracked gasoline with 50% by volume of a 27.5

to 400 F. cut of' naphthenicnaphtha obtained from Mirando crude. Theoctane number of this fuel was 72.3. Fuel 8 was prepared by blending 70%byvolume. cracked gasoline produced on-a combination high pressurecracking unit and 30% by volume of a ass-sir. cut of ard curves areintended to, apply only when using standard engine heads. The engineused in obtainingthe tests" shown in Figure 1 had a-standard head. Inall ofthe curves shown, those having-thehighest vertical position givethe best road performance. In Figure 1, curve 1 shows the standard sparkadvance setting for the particular car used in the tests. This car was awell-known .while the high speed portion of this curve occupies a highvertical position and hes well above curve I, thus indicating goodhighspeed performance,

the left-hand or low speed portion of the curve lies below curve 1,indicating that knocking performance would be obtained at low speeds.

Curve 3 shows the results obtained when using fuel 3. This fuelcontained a predominant proportion of oleflnsin the low boiling range; arelastraight run gasoline. This fuel had an octane number of 66.7. FuelE-19 was prepared by tively'low proportion of olefins in the highboiling range and a predominant proportion of aromatics in the highboiling range. It will be seen by the vertical distance between curve 2and curve I, that fuel 3 has superior performance qualities throughoutthe entire speed range, the superiority of fuel 3 being most pronouncedin the low speed range. Fuel 3 would not cause knocking in this car atany speed and could satisfactorily be used in an engine of unusuallyhigh compression ratio.

Curve 4 shows that the high speed performance of fuel 4 is quitesatisfactory but that the low speed performance is unsatisfactory inthat a knocking operation was obtained when operating the engine atspeeds of about 700 to 1100,R.P. M. Although theoverall octane of fuel4, is fairly high, namely '71, unsatisfactory operation in the low speedrange was obtained. This can be accounted for by the fact that the lowboiling portion of this fuel contains only 21% of olefinic hydrocarbons,the remainder of the fraction being parafllnic hydrocarbons. The highboiling portion of the fuel contains only a small amount of oleflns,namely, 9% and contains 42% of arcmatics and, therefore, produces asatisfactory high speed performance in spite of the unsatisfactorycomposition of the low boiling portion of the fuel.

Curve 5 shows that fuel 5 has excellent performance characteristics atboth high and low speeds and would not cause knocking in this engine atany speed. This fuel contains 73% by volume of olefins in the lowboiling portion and is, therefore, particularly well adapted to producegood-operating characteristics in the low speed range. The high boilingportion contains only 23% olefinic hydrocarbons, the remainder beingnaphthenic and aromatic hydrocarbons.

This composition in the high boiling portion of the fuel produced anexcellent high speed operation.

The car used to obtain the tests shown in Figure 2 was a standard makeof car equipped with a special distributor and a special head. Standard45 equipment included 14 mm. spark plugs. The compression ratio of theengine was 8 to 1. The tests represented by the curves in Figure 2 wereobtained under different climatic conditions and in an entirelydifferent car having a diiferent compression ratio than those shown inFigure 1 and the data in the two figures are, therefore, not directlycomparable. Fuels 4, 4b and 4c are all identical as to the hydrocarbonbase stock employed, fuel 4 being the clear unleaded fuel, while fuels4b and 4c are blended fuels containing lead tetraethyl. Similarly, fuels8, 8b and 8c are identical as to the hydrocarbon base stock employed,fuel 8 being the clear unleaded base stock and fuels 8b and 8ccontaining lead tetraethyl. The amounts of lead tetraethyl added and theoctane, numbers of these fuels are shown' in Table H.

T6518 II illctsne Cos. of lead Fuel-No. tetra-ethyl $22? 1 per method ono 0.5 77.2 1.5 82.0 o 66.7 0.5 69.8 1.5 74.1

It will be noted from the data in Table n that cated in Table I. Thedata there indicate that.

fuel 8 is much higher in those components which are generally acceptedas having higher lead susceptibility. Fuel 8 is higher in parafllnhydrocarbons and is much lower in aromatic hydro carbons, the latterbeing generally regarded as having inferior lead susceptibilitycharacteristics.

The improvement in road performance of fuel 4 effected by the additionof lead tetraethyl, as indicated by the borderline knock test curvesshown in Figure 2, is even greater than the improvement in octanenumber. A comparison of the vertical distance between curves 4 and 4bwith the vertical distance between curves 8 and 81), clearly shows thatthe road performance of fuel 4 was improved much more by the addition of0.5 cc. of lead tetraethyl per gallon than was fuel 8. The addition ofthis amount of lead improved fuel 8 only very slightly, the improvementbeing entirely confined to the high speed range, whereas the same amountof lead improved fuel 4 over the entire speed range, although theimprovement was much greater at speeds of 1500 R. P. M. and higher. Asimilar but even greater difference may be noted by comparing curves 4and 40 with 8 and 8c. The improvement efiected by the addition of 1.5cc. of lead tetraethyl per gallon in fuel 4, as indicated by thevertical distance between curves 4 and 4c, is many times greater thanthe improvement effected by adding the same amount of lead to fuel 8, asshown in curve 8c.- Thus; equivalent amounts of lead tetraethyl improvedfuel 4 vastly more than the improvement effected by equivalent amountsof lead tetraethyl in fuel 8. This degree of susceptibility toimprovement by the addition of lead tetraethyl, is of great importancein preparing commercial motor fuels. A further point which is broughtout by these'curves is the fact that although 1.5 cc. of leadtetraethylper gallon in fuel 4 produced substantial improvement in boththe high speed and low speed ranges, whereas the addition of the sameamount of .lead tetraethyl to fuel 8 produced scarcely any improvementup to speeds of 1000 R. P. M. This is due tothe fact that the lowboiling portion of thefuel contained 79% paraflinic hydrocarbons,whereas it has been found that to obtain superior low speed performance,the low boiling portion of the fuel must be predominantly olefinic incharacter. The high speed performance obtained with fuels, 8, 8b and 80was greatly inferior to that obtained with fuels 4, 4b and 40,

this fraction of 'fuel 8 contains higher proportions of naphthenes thandoes fuel 4 and as previously mentioned, these materials are generallyconsidered to have better lead vsusceptibility than aromatichydrocarbons. However, the higher proportion of aromatic hydrocarbons infuel 4 actually aided in producing a much higher road performance leadsusceptibility. This, eifect is fuels containing predominant proportionsof oleprovementin the low speed performance is-parprovement in low speed.performanceeifected by I the addition of the same amount of lead tetra-'aaeasec even more noticeable in those fuels in which the low boilingfraction contains a preponderance of oleflnichydrocarbons.

The unusual road rating lead susceptibility of flnic hydrocarbons in thelow boiling fraction and -dominant proportions of aromatics in the highboilingv fraction, the high boiling fraction containing not more thansmall proportions of 'oleflnic hydrocarbons is clearly brought out inFigure 3 which shows a comparison of the data obtained when using fuels13-19 and 13-20. The

car used to obtain the tests shown in Figure 3 was also a standard modelof a widely distributed and well-known brand, although not produced bythe same manufacturer as the car employed in obtaining data shown inFigures 1 and 2. The car employed in'obtaining the data shown inIFig'ure3 was equipped with a special head and had a compression ratio of 8.2to. 1.. Fuels 0 designated as E-19, El-19b and E-19c are all identicalas to the hydrocarbon base stock employed; fuel E-l9 beingthe clearunleaded fuel while fuels E-l9b and E l-19c are blended fuels containinglead tetraethyl. Similarly, fuels E-20,

. E-b and E-20c are identical as to the hydrocarbon base stock employed;fuel Ill-20 bein the clear unleaded base stock and fuels E-20b and E-20ccontaining lead tetraethyl. The amounts of lead tetraethyl and theoctane numbers oi these fuels are shown in Table III.

Table Cos. of lead tetraethyl per gallon It will be noted from the datain Table III that the lead susceptibility of fuels E-l9b and E-19c issuperior to the lead susceptibility of fuels iii-20b and 12-200,respectively. This is presumably due to the high paraiiin content offuels E4911 and iii-19c since it is well known that parafllnichydrocarbonagenerally speaking, show a superior lead susceptibility tocomparable hydrocarbons of the olefinic, naphthenic or aromatic type.However, a comparison of the road performance tests shown in Figure 3shows that the performance of fuels E-20,-E-20b and 15-20:: are ingeneral superior to the performance of. fuels E-19, E-l9b and E-19c,respectively. Note, for example, that the low speed performance of fuelE-20 is considerably better than the low speed performance 'of fuel E19, although the overall octane number of these two fuels is;substantially the same. The addition of 0.5 cc. of lead tetraethyl tofuel E-20 improved the performance of this fuel over the. entire speedrange. The imtlcularly conspicuous in comparison with the im- T ethyl tofuel E-19. A comparison of the-low speed range 01'- fuels E-20b andIii-19b shows that E-20b To is far superior to' fuel lit-19 ln thlscritical low speed range which is the range in which the greatest amountof difllculty with knocking per- A'ormance in actual operation'isordinarilyob- 5 vails in the low speed operation obtained with fuelsE-20 a and E-19c, the low speed performance of fuel E-20c being vastlysuperior to theperformance obtained with fuel E-19c in the same speedrange. The unusual road rating lead susceptibility of fuel E-20 is dueto the particular combination of hydrocarbons employed in the lowboiling and highboiling portions of this fuel. It is only when fuelscontain predominant proportions of oleflns in the low boiling range incombination with dominant and preferably 'preponderating proportions ofaromatics in the high boiling portion that such unusual road rating.lead susceptibility is obtained. IAS previously pointed out, the highboiling portion of the fuel must also contain not more than a minoramount such as 10% or 25% of olefinic hydrocarbons.

The particularproportion of unsaturated hydrocarbon components which itis desired to have present in the low boiling fraction of the fuel andthe maximum amount of unsaturated aliphatic hydrocarbon components whichmay be tolerated in the high boiling fraction of the fuel 4 may bevaried between rather wide as long as the unsaturated hydrocarbonspreponderate in the low boiling fraction and the unsaturated aliphaticsdo not exceed a minor portion in the high boiling fraction. Particularlyeffective results have been obtained when the low boiling fractioncontains a minimum of'about olefins and the high boiling fractionpreferably con.- tains not over about 25% unsaturated aliphatichydrocarbons by volume and preferably a maximum of about 10% unsaturatedaliphatic hydrocarbons. The high boiling fraction ,is preferably ofrelatively high octane number, that is, not less than about 50.Unusually .good fuels are those fuels which contain not more than theaforementioned proportions of unsaturated aliphatic hydrocarbons in thehigh boiling range and in which-the high boiling. fraction is composedpredominantly or substantially of alkylated benzenes. Increasedpercentages of the components indicated in each case ordinarily producefurther improvements. Under present manufacturing conditions it isneither economical formance. It is possible to effect :these unusualresults either by adding hydrocarbon compounds I of the desiredcharacter and boiling range to motor fuels or by appropriatefractionation and thermal treatment of hydrocarbons and employ ing thehydrocarbon mixtures thus produced. Smallamounts of lead tetraethyl areunusually effective in improving the road performance of the preferredfuels. For a given octane rating, whether it be high or'low, motorvfuels, the com- Position-of whichnhave been controlled in accordance'with this invention produce vastly superior', performance inthe spark ignition type of internal combustion engines, In general, itis preferred to have a minimum of approximately 65 octane number in theunleaded motor fuel in order to securemost effective results in internalcombustion 8118111158.!10W commercially prevalent. Although theinvention has been described in connection with specific details ofcertain embodiments thereof, it isnot intended that such details shallbe consideredas limiting the scope ,tion is approximately 52% volume ofsaid fuel constituting a fraction boil-' of the invention except insofaras indicated in the following claims.

We claim:

1. A motor fuel consisting substantially only of mono-olefinic,parafiinic, naphthenic and aromatic hydrocarbons approximating gasolinein boiling range in which the fraction boiling up to approximately 140F. comprises 8F-30% by volume of the fuel and contains a minimum of 80%of mono-oleflns, the fraction boiling above about 235 F. comprises35-70% of the fuel by volume and contains 50% or more alkyl benzenes,not more than 10% olefins and the balance saturated hydrocarbons, andthe overall octane of the fuel is more than 65.

2. A hydrocarbon motor fuel of gasoline boiling range consistingsubstantially only of monoolefinic, paraflinic, naphthenic and aromatichydrocarbons, the portion of said fuel boiling up to about 140 F.comprising from 8 to 30% by volume of said fuel and containing more than50% of mono-oleflnic hydrocarbons, the portion of said fuel boiling fromabout 140-235 F. comprising from 20-50% by volume of said fuel and thefraction boiling above about 235 F. comprising from 3570% by volume ofsaid fuel and containing at least 30% of alkylated benzene hydrocarbons,less than 25% of oleflnic hydrocarbons and the balance saturatedhydrocarbons, said fuel having an over-all A. S. T. M. octane number ofnot less than 65.

3. A motor fuel in accordance with'claim 2 in which the fraction boilingabove 235 F. contains less than 10% by Volume of olefinic hydrocarbons.

4. A motor'fuel consistingof parafilnic, naphthenic, mono-oleflnic andaromatic hydrocarbons, approximately 17% by volume of which hydrocarbonsconstitutes a fraction boiling up to 140 F., the mono-olefinic contentof which fracby volume, 25% by ing from approximately 140-235 F. andapproximately 59% by volume of said fuel constituting a fraction boilingabove about 235 F., said last mentioned fraction containing about 51%volume of aromatic hydrocarbons, about 8% by volume of oleflns and theremainder saturated hydrocarbons. said fuel having an A. S. T. M. motormethod octane number of 73.5.

5. A hydrocarbon motor fuel of gasoline boiling range substantially freeof hydrocarbons other than mono-olefins, paraflins, naphthenes andaromatics, the fraction boiling up to about 140 F. constituting from 8to 30% by volume of the fuel and containing more than 50% monoolefins,the fraction boiling between about 140 and 235 F. constituting from 20to 50% by volume of the fuel and .the fraction boiling from about 235 F.to the end point constituting from 35 to 10% by volume of the fuel andcontaining less than 25% by volume of olefins and a predominant amountof alkyl benzenes, theoctane number of the fuel being not less than 65.

6. Motor fuel in accordance with claim 5 in which the fraction boilingfrom about 235 F. to the end point contains less than 10% by volume ofoleflns.

'7. A motor fuel consisting substantially only of mono-olefins,naphthenes, paraffins and aromatics within the gasoline boiling range inwhich the fraction boiling up to about 140 F. constitutes about 22% byvolume of the fuel and contains about 73% of mono-oleflns and thefraction boiling from about 235 F. to the end point of the fuelconstitutes about 45% by volume of the fuel and contains about 23% ofmono-olefins, the balance of said fraction consisting of naphthenes andalkyl benzenes, the octane number of the fuel being approximately 72.3.

8. A motor fuel consisting substantially only of mono-olefins',paraffins, naphthenes and aromatics within the gasoline boiling range inwhich the fraction boiling up to about 140 F. constitutes about 14% byvolume of the fuel and contains about 62% by volume of olefins, thefraction boiling between about 140 and 235 F. constitutes about 34% byvolume of the fuel and the fraction boiling between about 235 F. and theend point constitutes about 52% by volume of the fuel and contains about48% by volume of alkvl benzenes, about 16% by volume of oleflns and thebalance saturated hydrocarbons, the octane number of the fuel beingabout :3.

WILLIAM B. ROSS.

